An online social network uses computer technology to help build and document social relations among people who share interests and/or activities. Social networks can facilitate communication between a large number of people. Some of the most popular social networks have tens of millions of users; the FaceBook® social network service (mark of FaceBook, Inc.) has over five hundred million registered users. It is not unusual for an individual user to have direct links in a social network to hundreds or even thousands of other users.
A social network often includes a representation of each user, such as a profile created by the user, containing self-provided information, information posted by other users, and links to other users who are “friends” of the profiled user. Users can upload pictures, post blog entries, search for other users with similar interests, and create and share contact lists. Many social network services are web based, allowing users to communicate with each other over the internet through postings, email, and instant messaging. To help protect user privacy, social networks often have controls that allow users to choose who can view their profile, who can contact them, who can add them to a list of contacts, and so on, but communications between users are not necessarily encrypted or otherwise protected as a result.